Even so, one part of Apple’s business wasn’t so positive: its iPad tablet. Apple sold 21.4m of them in the last three months of 2014 compared to 26m in the last quarter of 2013 – a 17.7% drop.

The company wasn’t alone. Research firms IDC and Canalys have both claimed that global tablet shipments were down year-on-year that quarter – the first such decline since Apple reignited the tablet market in 2010.

Both agreed on the general trend: manufacturers are shipping fewer tablets, and by extension, people are buying fewer of them. But why? Here are the main reasons.

1. Tablet buyers are hanging on to them for longer

In 2010, no one was sure how often people would want to upgrade their tablets. Would it be every 12-18 months like a smartphone, or would their upgrade cycle be longer, and more like that of computers? Five years on, it’s becoming clearer.

“The upgrade cycle is longer,” said Apple chief executive Tim Cook, in his last earnings call. “It’s longer than an iPhone, probably between an iPhone and a PC. We haven’t been in the business long enough to say that with certainty, but that’s what we think.”

“The lifetime of tablets is being extended – they are shared out among family members and software upgrades, especially for iOS devices, keep the tablets current,” said Gartner research director Ranjit Atwal recently.

If you’re a mainstream tablet owner, chances are your device is mainly used for email, social networking, light web browsing and perhaps games and video streaming. Unless you’re into processor-stretching 3D games, none of those categories provide a huge incentive to upgrade once a year.

2. Larger-screened smartphones are proving popular

The slowing growth and now decline in tablet shipments has come alongside the emergence of the “phablet” – larger-screened smartphones that first came to prominence from Android manufacturers, before Apple finally followed suit in the autumn of 2014.

Think back to the mainstream tablet use cases listed earlier: a big smartphone can do a capable job at all of them. Especially as the boundaries between the two categories narrow.

Canalys estimates that in the last quarter of 2014, seven-inch tablets accounted for half of all Android tablet shipments – and noted that these are exactly the devices most under threat from larger-screen smartphones.

Meanwhile, even Apple’s keenest customers may have stopped and thought about a new iPad purchase in the final months of 2014, given the launch of the iPhone 6 and 6 Plus. IDC’s senior research analyst, Jitesh Ubrani, saw the “excitement around the launch of the new iPhones” as a key factor in iPad’s tough quarter.

3 . Laptops are also competing

Tech journalism traditions dictate that every new product category must “kill” another one. In the case of tablets, netbooks seemed the likeliest victim back in 2010. However, their larger laptop cousins have proved a tougher rival in the years since.

If fewer techy potential tablet owners are finding that a phablet can cater to their needs, so the more techy ones may be finding the lure of a laptop hard to resist. Given that these people are also likely to have large-screened smartphones, a tablet may seem like more of a luxury device.

“There is probably some level of cannibalisation that’s going on with the Mac on one side and the Phone on the other,” said Cook after the quarter during which iPad sales dipped, but sales of Mac laptops saw “double-digit” growth. “I’m sure that some people looked at the Mac and iPad and decided on a Mac,” Cook told analysts in the company’s last-but-one earnings call. “And I am fine with that by the way.”

Cheaper Chromebooks and an aggressive push for “Windows with Bing” laptops were also factors as 2014 drew to a close – the latter in particular, according to Canalys.

“The new price points it enabled stimulated notebook demand in established markets in Western Europe and the US. This will have hurt tablet sales in these markets in the fourth quarter as consumers opted to replace ageing consumer notebooks,” said research analyst Jason Low.

4. Samsung and Amazon have been struggling

Apple wasn’t the only tablet maker to ship fewer devices in the final quarter of 2014 than the same period the year before. IDC estimated that Samsung’s shipments fell 18.4% to 11m units, with Ubrani suggesting its struggles proved that “mid to high-priced Android tablets simply aren’t cut out for today’s tablet market”.

On the face of it, Amazon had an exceptionally bad final three months of the year too: IDC claimed that its shipments fell from 5.8m to 1.7m units year-on-year – a 4.1m drop in a quarter when the company estimated that the overall market was down by just 2.5m units.

Amazon dragging everyone else down? Not so much: IDC didn’t count shipments of the company’s new six-inch Fire HD tablet, because the screen size didn’t match its definition of a “tablet”. Canalys claimed that Amazon shipped 4m tablets during the quarter, by contrast.

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Both companies faced the challenges listed earlier though, with Amazon particularly focused on the kind of mainstream tablet users who would be most likely to balk at replacing the tablet they bought a year before so soon.

5. Has there been a lack of innovation?

The final theory doing the rounds about why tablet shipments are falling is the suggestion that 2014’s crop of new models lacked genuinely exciting and innovative new features to persuade people to get their wallets out.

Gartner’s Atwal described this as “the lack of innovation in hardware which refrains consumers from upgrading” in a year when new devices from Apple, Samsung, Amazon and their rivals were mostly iterative in their improvements over previous models.

There is no firm opinion on what improvement would be capable of kicking some life back into tablet sales, though. Twelve-inch displays? Haptic feedback? More niche tablets aimed at specific groups like children, gamers or designers?

Perhaps software will be the key: smarter Siri-style virtual agents to anticipate our needs, or tools to make tablets the heart of our increasingly-connected homes. Or perhaps the next big uplift in tablet sales will be about marketing: selling more to schools and businesses.